Rhesus Cytomegalovirus (RCMV). Severe congenital infection and disease are produced in rhesus fetuses inoculated intraamniotically or intracerebrally with RCMV. Lesions confined to the CNS consisted of ventricular dilatation, leptomeningitis choroid plexitis, ependymitis and focal encephalitis. Ventricular dilatation appears to be the result of severe tissue destruction of the subependymal area since ventricular obstruction is not present. This model will be useful in the study of the pathogenesis of congenital CMV infections. Group B Streptococci (GBS). Maternal immunization may not be the best means to protect the fetus. We found maternal humoral immunity insufficient to prevent GBS infection of the rhesus monkey fetus. Therefore, treatment of the newborn infant with hyperimmune human IgG was studied. Results indicate that severe GBS infection in the rhesus newborn can be treated successfully with hyperimmune immunoglobulin. Our findings have since been used to justify the treatment of infant humans infected with GBS. SAIDS. Polymyositis developed in 50% of the rhesus monkeys that developed clinical signs of SAIDS. The morphologic features of polymyositis in the monkey are identical to those seen in human polymyositis. We suspect a possible association between a human retrovirus and some cases of polymyositis in man. Varicella-Zoster. A new strain of simian varicella-zoster virus has been isolated from a rhesus monkey (Macaca mulatta) with a typical chickenpox-like illness. This new strain of virus has potential use for establishing an animal model of human varicella-zoster.